I found this prompt on fanfiction.net, it's not mine so you can use it. The idea thing is mind it's just the first sentence in italics that's the prompt.

"My feelings aren't Quaffles, you can't just throw them around whenever you please and expect me to enjoy it!"

'Morning, Lily,' James yawned, coming out of his bedroom and into their shared common room. 'Sleep well?'

Lily looked up, wondering exactly when it had become a regular occurrence for them to call each other by their first names and ask each other if they slept well and when she'd started to like it.
'The usual,' she replied. James knew what the usual meant- he was usually the one running into her room and comforting her when she woke up screaming, after all. 'What about you? I didn't hear you in the night.'

James winced. Lily also came into his room at night and murmured soothing words into his ear when he woke up screaming his friends and families names, along with 'Voldermort' and 'don't hurt them, please don't hurt them, take me, take me instead!'

'I slept well enough,' he replied, closing his eyes. Lily noticed the shadows under his eyes, the way his hands clenched into fists, his messier than ever hair and rumpled clothes.

'James,' she said quietly, moving to stand next to him. 'James, are you okay? You look exhausted.'

'I'm fine, Lily, I'm fine.' He gave her a tired smile, running a hand through his hair as he did so.

Lily caught his wrist as he moved his hand down to his side. 'James,' she said in a low voice. 'James, you can trust me. Whatever it is, we can-'

'My feelings aren't Quaffles, Lily, you can't just throw them around whenever you please and expect me to enjoy it!' James burst out. 'You- sometimes you're like this, you're kind and you talk about we and you help me when the nightmares become too much, but other times you're the Lily I knew in first year, who rolls her eyes at me and turns up her nose when I walk past- please, be one or the other! I can't stand thinking you might like me sometimes and then other times thinking you hate me and you'd be glad if a stray curse finished me off-'

'James!' Lily tried to say, but he wasn't finished.

'Please, tell me the truth! Sometimes when I'm terrified, you're there, sleeping next to me, and I think I'm dreaming because the next morning you're gone, like a ghost, and maybe it is a dream, apart from sometimes I find red hairs on the pillow, and I think maybe you do care about me after all, but then you act like it's back to first year and James-and-Lily from six years ago, and I wish you would just tell me how you feel.'

He looked down at her, running his free hand through his hair. 'Merlin,' he muttered. 'I didn't mean to say all that-'

Lily realised she was still holding into his hand and dropped it, her face turning red. 'No, I mean, it's fine. I have some things to say, too.'

She took a deep breath. 'You used to ask me out almost every day for six years, until you became Head Boy and you stopped. I felt worried- had I become less likeable over the summer? And that's when I realised I liked you. Why else would I be bothered about you asking me out or not? Then we had to share a common room and had rooms next to each other, where we'd be only a wall apart, and I thought shit. I'd be able to hear you and your Marauders all the time. But that first night I had nightmares and woke up screaming and you came and just hugged me and told me I was safe, we'd be safe, we'd make it through this war, I realised that I might more than like you. And I felt scared.'

Lily couldn't stop. The words flew out of her, the words she hadn't told anyone- words she'd barely thought herself.

'So I acted like the old Lily again. I pretended to hate you. I didn't need any more people to care about, for You-Know-Who to use against me in this goddamn war. Then two days after that, you yelled in your sleep. I woke up and went over to your room- you were asleep, and you cried out don't hurt them, please, take me instead. Do whatever you want to me, just don't hurt them. And yes, I slept next to you and left the next morning, wondering what to do. I couldn't car about you, because if you got hurt or-'

Lily bit her lip.

'Died. If you died, how would I cope? I kept changing my mind. I keep changing my mind. Whenever you cry out in your sleep, I come into your room and try and help. And I try not to care so I'm not hurt, and, goddamn it, it doesn't work. I care, James. About you.'

James stared at her, eyes wide.

Lily tried to laugh. 'I mean-'

'Please tell me this isn't a dream,' James whispered.

'It isn't,' Lily replied quietly. 'I know it isn't. I don't have dreams as nice as this.'

And he kissed her- or she kissed him- and it was Lily-and-James and James-and-Lily.

Them against the world.

'Til death do us part.

Mostly speaking sorry

It felt much better when I was writing it sorry